The invention relates to an anastigmatic anamorphic lens unit for processing images, particularly multidimensional images, as they are generated and evaluated, for example in connection with spatially resolved spectroscopy.
Using an anamorphic lens, spatially resolved spectral images can be depicted on sensor arrays using different lateral image scales.
An anamorphic lens system or “anamorphot” produces a “distorted image” by way of different image scales in two orthogonal directions. The ratio of these two image scales is referred to as the compression ratio, aspect ratio, anamorphic ratio, or anamorphic lens factor.
Anamorphic lens systems are used in image processing, primarily for taking and projecting motion pictures and static pictures. These applications are directed at taking into consideration the psychological visual perception of the person, and/or an effectively utilizing the footage and/or digital data media.
The design of an anamorphic lens is generally based on a previously corrected rotationally symmetrical base lens unit, which is combined with one or two more lens units, each comprising uniformly oriented cylindrical lenses.
A compact two-piece anamorphic lens for the digital projection of electronically produced images is known, for example (DE 10060072). The basic arrangement comprises a front anamorphic lens unit having two cylindrical subcomponents with high refractive power in the horizontal direction and a spherical projection lens unit at the center, and a rear anamorphic lens having one or more cylindrical lenses with low refractive power in the vertical direction and a negative focal length.
A further three-piece arrangement, for example for taking pictures with a process camera, is known from the printing industry (U.S. Pat. No. 3,871,748), wherein two afocal cylindrical lens systems are disposed, in front of and behind a rotationally symmetrical lens unit. In the literature, further combinations of spherical and cylindrical lens units are described, wherein the cylindrical and rotationally symmetrical spherical units are corrected independently of each other.
One patent (DE 199 11 862 C1) differs from this design principle, and particularly from an automatically corrected base lens unit. Here, “conventional” cylindrical lens systems are combined with special spherical base lens units, which still have aberrations, which have not been corrected, and which, together with the aberrations of the cylindrical lens units, improve the quality of the image.
Furthermore, an anamorphic attachment for recording and reproduction purposes has been described (DE 41 04 684 C1), which comprises a lens group encompassing both spherical and cylindrical surfaces.
Furthermore, an anamorphic converter is known, which is suitable for converting a digital 16:9 (1.78:1) film format to the conventional 2.35:1 format using a compression or aspect ratio of 1.252:0.947 (anamorphic factor 1.322), while largely avoiding the formation of ellipses (U.S. Pat. No. 6,995,920 B2).
All of these examples and principles have in common that the individual sub-systems are initially configured independently of each other, and that compression or aspect ratios (anamorphic factors) of 1.3:1 (1.3) to 2:1 (2) are substantially not exceeded, or that, during conversion, aspect ratios in the opposite direction of 1:1.3 (0.77) to 1:2 (0.5) are substantially met. While correction of aberrations and astigmatism is desired, it is possible only with limitations, due to the respectively separate observation of individual systems. Requirements for the imaging behavior of the anamorphic lens in conjunction with a well-corrected image, which are collectively extremely high, and which arise, for example, in spatially resolved spectroscopy, mean that the procedure that was common when designing such systems, and which corresponds to the prior art, can no longer be followed. FIG. 5 illustrates the principle of spatially resolved spectroscopy, which is known per se. Here, photographs of planar elements located in an object region (on the outside left in FIG. 5) typically must be reproduced in two-dimensional spectral images such that one direction constitutes the spatial resolution and, orthogonal thereto, the second direction constitutes the spectral resolution (on the outside right in FIG. 5). Processing of the image, which is advantageous for a faster evaluation, is carried out with a dispersive lens unit, which is disposed between the plane elements and a sensor array illustrated as a lattice, and comprises the anamorphic lens.
Depending on the lens unit producing the spectral image, both directions may have markedly different image scales, which must be represented for any further evaluation, such as on the sensor array having a fixed geometry. The different image scales of the spectral image and the representation of such multidimensional spectral images on sensor arrays that differ markedly in terms of the two dimensions of width and height, result in great difficulties when designing the correspondingly required anamorphic lens.